[1] The date of Edward Steinkopff's death is given in the Knoedler prospectus, in NGA curatorial files. A sale of the collection of "the late Edward Steinkopff" took place on 26 February 1909 at Christie's in London. Steinkopff's daughter (and only child) was married in 1899 to James Alexander Francis Humberston Stewart-Mackenzie, who was created the 1st baron Seaforth in 1921 and who died in 1923.

[2] A photograph in the archives of the Museo di Castello Sforzesco in Milan (no. 2430 D; a print is also preserved in the photographic collection of the Kunsthistorisches Institut in Florence) shows the NGA painting repainted, probably after suffering a radical cleaning most likely having occurred at the time of the change in ownership in the mid-1930s. The photograph probably dates before 28 April 1936, when the director of the museum in Milan, Giorgio Nicodemi, wrote a letter (in NGA curatorial files), documenting the fact that the painting, which he hoped would be donated to the Castello Sforzesco, had already been shown to him. According to a note attached to the negative of the photograph in the photographic archive of the museum, the painting, owned by the family of the barons of Castelmuro, was at that time (1935) exhibited at the Museo Navale in Milan.

[3] See Knoedler stock book no. 8, p. 156 and Knoedler sales book no. 13, p. 366, M. Knoedler and Co. records, Getty Research Institute, Los Angeles (copies NGA curatorial files). According to a letter from R. Heinemann, Lugano, to C. Henschel of the firm M. Knoedler & Co., New York (copy in NGA curatorial files), the painting was shipped to New York on 29 April 1936.

[4] The date of purchase is given in the Mellon collection records, in NGA curatorial files.